Connecting to Internet via Router

Hi, I'm new to this forum so I hope I am doing this correctly. I am having a problem connecting a computer to the internet via a router...
I have DSL now. I just moved from a place where I had cable modem and router connection and didn't have this problem. Now, with DSL setup, the router is connected to the modem and I already have tried 2 other pc's connected to the router and both have connected fine to the internet.
However, I have a another computer that won't seem to connect to the internet and I'm not sure why. Could it be a faulty part??? It is a Dell, about 2 years old (I can get the model info if necessary) with Windows XP. I am using a ethernet cable and the green and yellow light on the NIC card are on when I try to connect. I noticed the fan is going on and off and won't run steady but found out that has been going on for awhile so I don't think that has anything to do with it?? Could it be virus related?? Any suggestions would be greatly appreciated!

What type of router do you have? Is your router running NAT and DHCP? Are your TCP/IP settings correct? Can you ping(from the command prompt) the other computers on your LAN? Compair the problem PC's "ipconfig" to the other pc's. I'm not being condesending but here are some paths and command statements for the trouble shooting utilities I just mentioned.

COMMAND PROMPT: START>RUN>type(CMD)
For an ip configuration type:ipconfig or ipconfig/all
For ping: ping xxx.xxx.xxx.xxx(IP address)
See if you can ping other pc's, then ping what they have listed as "gateway" in in their ipconfig (this should be the LAN/inside interface ip adress of your router)
Then try and ping an outside/internet address.

If you need to, just pull the ipconfigs and try and ping the adresses. Then copy/paste them in here with decriptions of which pc they came off of.

were you running both of the other pcs at the same time.
Two things you should know about DSL versus Cable.
Cable is easy.
DSL requires a user name and password.
It also requires you to edit the settings in the dsl modem so the router can funtion properly.

Have you done all this?

Can you get to the router on each of the machines whether you can get to the internet or not?

The way to get to the router is to do the ipconfig thing and look at your gateway.
Then take the gateway address and put that in your internet explorer address bar.